1. Field of the Invention
The present invention is generally related to float switches and, more particularly, to a float switch which incorporate a single-piece pivotable device which moves a permanent magnet along an arcuate path in response to changing levels of a fluid within a containment.
2. Description of the Prior Art
Many different types of fluid level sensors are well known to those skilled in the art. Some of these devices utilize a buoyant member which is moved in response to a changing liquid level. The movement of the buoyant member is typically utilized to activate a switch or a valve mechanism.
U.S. Pat. No. 5,250,768, which issued to Van Fossen on Oct. 5, 1993, discloses a float switch with a snap action member. The switch is intended for sensing a liquid level and then switching its state in response to changes in the level. The device is carried within a hollow housing with its movement being restrained by the tethering action of a power cord. Snap action switching is achieved by the interaction between an actuator having camming surfaces formed on its exterior and a spring loaded switch mechanism. The mechanism includes a thin, flexible E-shaped snap member having two legs bowed to form a leaf spring and having a bearing point located on the central leg.
U.S. Pat. No. 5,134,729, which issued to Shaw on Aug. 4, 1992, describes a positive shut off, metered control system for use with flush toilet tanks. The device is intended for metering the flow of water into the tank and bowl of any currently known tank toilet and providing positive shut off of the flow. When the toilet handle is turned, a linkage rotates a cam to force a stopper from its seat. This action commences water flow. The water flows through a flow channel to be directed by a flow nozzle past a water wheel imparting a rotation thereto. The water wheel is gearably linked to the cam thereby rotating the cam. When the cam has rotated to position a cam repeat over the stopped stem, the stopper is receipted by the pressure of the water and water flow ceases.
U.S. Pat. No. 4,917,795, which issued to Sable et al on Apr. 17, 1990, discloses an automatic valve assembly with an improved automatic air pressure relief and check valve assembly which can be used in combination with a swimming pool filter tank or a swimming pool separation tank. The valve assembly includes a normally open lower valve which communicates with the inside of the tank and is responsive to the tank's being full of pressurized water for closing the lower valve. The valve assembly further includes a normally closed upper valve communicating with the lower valve and the outside of the tank. The upper valve is responsive to air being expelled from the tank through the open lower valve when water is refilling the tank. Cooperating with the upper and lower valve of the improved valve assembly is a means for precluding both the upper and lower valves from being simultaneously maintained in their closed positions.
An article, titled "MOLDING MASTERPIECES", by Richard J. Babyak in the November 1993 issue of Appliance Manufacturer, describes a low pressure molding technique which provides certain advantages in the manufacture of injection molded components. The article describes several molding techniques that are made possible by a particular low pressure molding process. One of those techniques is described as a dual density process that yields sandwich moldings having a hard and compact skin and an expanded cellular core that are both made of the same resin on the same injection molding device. This technique is described as providing rigidity and thickness while minimizing weight and resin costs. Although this particular technique is not described in significant detail in this magazine article, it appears to relate to the use of two different moldings sequentially manufactured on the same injection molding machine to result in a hard skin layer surrounding a lower density core. It is believed that the term "sandwich" implies this construction. Nothing in this article describes a technique for manufacturing a single piece component that has a low density portion and a higher density portion that are formed during a single injection process.
U.S. Pat. No. 4,864,665, which issued to Toltzman on Sep. 12, 1989, describes a dual flush system for toilets. The system is intended to effect a partial or mini-flush of the toilet to carry away liquid waste by partially opening the main valve situated in the water holding tank of a toilet for a period of time determined by an operator. The described device provides a means for the upward lifting of the main valve by limiting the rotational movement of the lever arm connected to the main valve by a cord or chain. Upward movement of the lever arm is limited within the flush handle assembly connected to the lever arm. A partial flush handle movement is terminated by sticking a modified excentrically shaped cam situated within a hollowed-out cavity in the partial flush handle and a full flush handle is provided to continue raising the lever arm to effect a full flush.
The principle of using a buoyant member to respond to changes in water level and thereby actuate a switch or a valve is known to those skilled in the art. This type of device has been used to control the water level in toilet tanks for many years. Devices of this general type are also used in apparatus, such as dishwashers, for the purpose of determining when a particular fluid container needs to be refilled. For example, the container may be intended to hold dish washing detergent or other fluids for use during the dish washing cycle.
For use in certain applications, it is necessary to provide a rugged fluid level sensor which also provides an accurate indication of the level of a liquid. Furthermore, it is advantageous to provide a liquid level sensor which is easily manufacturable. Several of these goals are achievable through the use of a single piece rotatable device having a buoyant portion and a magnet holding portion.